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Our future, our universe, and other weighty topics

Sunday, April 20, 2014

Faced
with the fine-tuning problem of why the universe seems to be so well calibrated to allow the existence of intelligent life, some thinkers
have advanced the idea of a multiverse, the idea that there is a vast
ensemble of universes. The thinking is that if there are an infinite
or nearly infinite number of universes, then we might expect one of
them to luckily have just the right conditions allowing for
observers. The drawbacks of this approach are many: the nearly infinite
baggage of assuming all of those universes, almost all uninhabited; the violation of
the principle of Occam's Razor asserting that “entities should not
be multiplied beyond necessity” when trying to explain something;
the violation of the principle of mediocrity asserting that a random
sample from a larger population should be assumed to be
representative of the population; the fact that we have never had a
verified case of anything being successfully explained by a
multiverse; the fact that while the probability of some universe
being habitable by chance may be improved by assuming other
universes, the probability of any particular universe (including our
universe) being habitable by chance is not at all improved by such an
assumption, not even by even 1 percent.

Perhaps
sensing the weakness of a simple multiverse theory, some theorists
have advanced a more complicated theory – a theory they call
cosmological natural selection. The idea seems to have first been
advanced by the physicist Lee Smolin (author of the excellent book
The Trouble With Physics). In his book Time Reborn,
Smolin describes the theory as follows:

The
basic hypothesis of cosmological natural selection is that universes
reproduce by the creation of new universes inside black holes. Our
universe is thus a descendant of another universe, born in one of its
black holes, and every black hole in our universe is the seed of a
new universe. This is a scenario within which we can apply the
principles of natural selection.

Smolin
claims to have a theory of how the physics of the universe could
evolve through natural selection. But how on earth can we get
anything like natural selection out of the idea of new universes
being created by the formation of black holes? Smolin gives the
following strained reasoning: (1) he claims that the physics that
favors a habitable universe are similar to the physics that favor the
production of black holes; (2) he claims that a new universe produced
by a black hole might have slightly different physics from its parent
universe; (3) he claims that random variations in physics that would
tend to produce universes that produce more black holes would cause
such universes to produce more offspring (more universes); (4) he
claims that as a result of this “increased reproduction rate” of
some types of universes, we therefore would gradually see the
evolution of physical laws and constants that tend to favor the
appearance of life and also the production of black holes.

First, let's look at the linchpin claim that a new universe can be
produced from the collapse of a huge star to form a black hole. Some
analysts let Smolin get away with making this claim, but there is no
reason why that should be done. The idea that a new universe can be
produced from the collapse of a black hole is a complete fantasy,
with no basis in fact. We have no observations to support such
a theory.

But
let's try to open the door to such an idea. What would it be
like if the matter in a collapsing star formed a black hole, and that
extreme density of matter caused the surrounding space to be pinched
off into its own little bubble? What would we then have? Such a
little bubble should not be called a new universe, as that gives a
completely misleading idea of some vast area with enough matter to
form many galaxies. The bubble would be properly referred to as a
spacetime bubble, or a micro-universe.

If
such a spacetime bubble were to be formed, what would happen to the
matter that was trapped in the black hole? It would be separated from
our universe permanently, sealed off in its own little realm. We
would no longer observe the gravitational effects of that matter in
our universe. We would observe that black holes do not exert
gravitational effects once they form. But that is not at all what we
observe in regard to black holes. Black holes continue toexert
very strong gravitational effects (such as sucking up all nearby
gas), just as if their matter continued to exist in our universe. In
short, our observations are in conflict with the idea that when a
massive star collapses to become a black hole, that matter exits our
universe to form another universe. Our observations indicate that the
matter lost in black holes is still here in our universe.

And
what if the matter in a collapsing star were to cause a new universe
when a black hole formed, and the matter moved over to that universe?
You would then have a tiny little one-star-sized universe. Such a
possibility is worthless in explaining our universe, which has the
mass of at least 1,000,000,000,000,000,000 stars.

Another problem with Smolin's theory is that it absolutely requires you to believe that our universe has been optimized to produce a maximum number of black holes -- a thesis that is rather implausible given the fact that the nearest black hole is no closer than 1500 light years away, and that only one in about 30,000,000 nearby stars is a black hole. In fact, other scientists maintain that the universe is not at all optimized to produce black holes.

Another
huge problem with Smolin's idea is that it does not explain how any
universe could have originally came to exist in the state in which
black holes could exist in it (a state similar to a state in which
life could exist in it), a state enormously improbable to occur by
chance. Although you may associate the concept of black holes with
ideas of chaos, randomness, or disorder, there are actually many requirements that any
universe must meet in order for it to have stars that can form into
black holes. Smolin lists 6 such requirements on page 36 of this paper, all of which are incredibly lucky long shots. Another
requirement is that the proton charge very precisely match the electron charge to many decimal places, for
unless you have that coincidence there will never exist the stars
from which black holes form.

In
our universe the proton charge and the electron charge match to at least eighteen decimal places, and there is every reason to think that
this fine balance is necessary for stars to exist. Imagine
if the proton charge and the electron charge differed by one part in
a trillion. That would be like increasing the electromagnetic forces
on a star by one part in a trillion. But the
electromagnetic force (one of the four fundamental forces) is about a
trillion trillion trillion times greater than the gravitational force (another of the four fundamental forces), which means
that even if there were a very tiny difference in the proton charge
and the electron charge (say, 1 part in a trillion), the resulting
repulsive force would be many, many times greater than the force of
gravity holding together stars, and stars could not hold together.
Greenstein (a professor emeritus at Amherst) says that the proton charge and the electron charge have to
be balanced to 18 decimal places for stars to exist.

So
let's imagine a collection or series of universes with random
properties. It would require an incredibly unlikely set of
conditions for any particular one of these universes to have the
conditions necessary to produce black holes – a long shot with
odds of no greater than 1 in a billion billion. According
to Smolin's theory, once such a universe existed it might begin
making copies of itself, as black holes formed new universes. So if
you started out with several billion billion universes, a
few might produce black holes, and then gradually (according to
Smolin's theory), the fraction of the universes that had black holes
(and that were compatible with life) might keep getting higher and
higher over the eons. Such a theory might comfort some people by
making our universe seem not so untypical in a collection of
universes. But it would do nothing to explain the original incredibly
unlikely long shot.

To
give an analogy, imagine you have a book-copying robot which is given
a copy of a rare and wonderful book, such as a first edition of
Dickens. Such a robot might then make 1000 copies of the book, and
stack them on your bookshelf. Seeing all of those copies on your
bookshelf, you might then tend to think that the original first
edition was not so rare and wonderful, but this machine would not at
all explain the origin of the first edition in the first place,
something that would be very hard to plausibly explain by any theory
of luck.

Smolin
claims that one advantage of his theory is that it makes a
falsifiable prediction, and in a 2004 paper (page 38) he lists one such
prediction:

There is at least one example
of a falsifiable theory satisfying these conditions, whichis cosmological natural
selection. Among the properties W that
make the theoryfalsifiable is that the upper
mass limit of neutron stars is less than1.6 solar
masses. This and other predictions of CNS have yet to be falsified,
but

they
could easily be by observations in progress.

But
in this 2010 Science Daily piece reported the discovery of a neutron star: “The
researchers expected the neutron star to have roughly one and a half
times the mass of the Sun. Instead, their observations revealed it to
be twice as massive as the Sun."

So
according to Smolin's own guideline, the theory of cosmological
natural selection has been falsified. He said it would be falsified
if we discovered any neutron stars greater than 1.6 solar masses, and
a neutron star with a mass of 2.0 solar masses has been discovered.

In
fact, this paper estimates that a particular neutron star called the
black widow pulsarhas
2.4 solar masses. In his book Time Reborn, Smolin concedes, “If
that finding holds up under more precise measurements, cosmological
natural selection will be falsified.”

It
would seem that the black widow pulsar has delivered a fatal bite to
the theory of cosmological natural selection, somewhat like a black
widow spider giving a fatal bite to a human.

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All posts on this blog are authored by Mark Mahin, and are protected by copyright. Copyright 2013-2014 by Mark Mahin. All rights reserved. Any resemblance between any fictional character and any real person is purely coincidental.